Investigation of static magnetic field effect on horseradish peroxidase enzyme activity and stability in enzymatic oxidation process

Incubation of Horseradish Peroxidase near 50 Hz AC Equipment Promotes Its Disaggregation and Enzymatic Activity

Low-frequency electromagnetic fields, induced by alternating current (AC)-based equipment such as transformers, are known to influence the physicochemical properties and function of enzymes, including their catalytic activity. Herein, we have investigated how incubation near a 50 Hz AC autotransformer influences the physicochemical properties of horseradish peroxidase (HRP), by atomic force microscopy (AFM) and spectrophotometry. We found that a half-hour-long incubation of the enzyme above the coil of a loaded autotransformer promoted the adsorption of the monomeric form of HRP on mica, enhancing the number of adsorbed enzyme particles by two orders of magnitude in comparison with the control sample. Most interestingly, the incubation of HRP above the switched-off transformer, which was unplugged from the mains power supply, for the same period of time was also found to cause a disaggregation of the enzyme. Notably, an increase in the activity of HRP against ABTS was observed in both cases. We hope that the interesting effects reported will emphasize the importance of consideration of the influence of low-frequency electromagnetic fields on enzymes in the design of laboratory and industrial equipment intended for operation with enzyme systems. The effects revealed in our study indicate the importance of proper shielding of AC-based transformers in order to avoid the undesirable influence of low-frequency electromagnetic fields induced by these transformers on humans.

Effect of magnetic field treatment on the softening of green chilies (Capsicum annuum L.) during storage

In this study, effects of magnetic field treatment on the softening of green chilies during storage (0-30 d at 10 °C) were investigated, and the cell wall polysaccharide content, modifying enzyme activities, water distribution, and cell wall structure were determined. After 30 d of storage, the weight loss of the green chilies in conventional refrigeration (CR) group reached 35.40 %, whereas it was 20.96 % and 29.85 % in the static (SMF; 4 mT) and alternating magnetic field (AMF; 4 mT, 1 Hz) groups, respectively. Furthermore, magnetic field treatment maintained low levels of water-soluble pectin (WSP) and high levels of chelate-soluble pectin (CSP) and sodium carbonate-soluble pectin (NSP) in the green chilies. The degree of methylation (DE) values of WSP and NSP in the pre-treated samples were 0.37 and 0.18, respectively. Conversely, at the end of storage, the DE values of WSP and NSP in the CR, SMF, and AMF groups decreased to 0.12 and 0.05, 0.25 and 0.11, and 0.18 and 0.07, respectively, suggesting that magnetic field treatment had a negative influence on the demethylation of pectin. Magnetic field treatment also decreased the activities of pectin methyl esterase, polygalacturonase, and β-galactosidase in the green chilies, maintaining them at a low level. The magnetic field treatment resulted in a higher free water content in green chilies compared to the CR, exceeding the CR group's content by 1.79 % and reaching 88.18 % at the terminal storage. Scanning electron microscopy results revealed that magnetic field treatment maintained the structural integrity of the cell wall in the green chilies. The results of this study confirmed the applicability of magnetic field treatment in maintaining the firmness and reducing the weight loss of the green chilies, thus prolonging their shelf life.

Effect of low-frequency alternating magnetic field on exopolysaccharide production and antioxidant capacity of Pleurotus citrinopileatus by submerged fermentation

The objective of this study was to investigate the effect of low-frequency alternating magnetic field (LF-AMF) on the production of extracellular polysaccharide (EPS) by submerged fermentation of Pleurotus citrinopileatus. The fermentation conditions optimized by the central composite design method were as follows: fermentation time of 6.18 days, temperature of 28.28 °C, shaking speed of 149.04 r/min, and inoculum amount of 8.43%. Under these conditions, a LF-AMF was applied to the submerged fermentation of P. citrinopileatus. When the intensity of LF-AMF was 40 Gs, the initial intervention time was 24 h after inoculation, and the treatment time was 6 h at one time, the mycelial biomass of P. citrinopileatus increased by 11.30%, and the EPS yield increased by 23.09% compared with the fermentation without LF-AMF treatment. The morphology of mycelium after LF-AMF treatment was observed by scanning electron microscopy. It was found that the surface of mycelium was wrinkled, and the structure of mycelium was loose, which might be more conducive to the production of EPS. Mycelium diameter decreased, and ATPase activity increased, indicating that LF-AMF had a positive effect on the production of EPS by P. citrinopileatus fermentation. Moreover, LF-AMF could improve the permeability of the mycelial cell membrane, facilitate the exchange of intracellular and extracellular substances, and increase the metabolic capacity of P. citrinopileatus. In vitro antioxidant test of EPS showed that LF-AMF treatment also improved its antioxidant capacity.

Comparative sensitivity of A-type and B-type starch crystals to ultrahigh magnetic fields

In this study, maize starch (A-type) and potato starch (B-type) were treated with ultrahigh magnetic fields (UMF) of different intensities (5 T and 15 T) to investigate their sensitivity to UMF by measuring changes in their structure and rheological properties. The results indicate that the crystallinity of A-type starch significantly decreases, reaching a minimum of 20.01 % at 5 T. In contrast, the crystallinity of B-type starch significantly increases, peaking at 21.17 % at 15 T, accompanied by a brighter polarized cross and a more perfect crystal structure. Additionally, B-type starch exhibited a significant increase in double helix content (from 32.67 % to 42.07 %), branching degree (from 1.96 % to 3.84 %), and R1022/995 (from 0.803 to 0.519), compared to A-type starch. B-type starch also showed a greater propensity for cross-linking reactions forming OCOR groups (from 0 % to 6.81 %), and its enthalpy change (∆H) increased substantially (from 19.28 J/g to 31.70 J/g), indicating a marked enhancement in thermal stability. Furthermore, the average hydrodynamic radius (Rh) decreased more for B-type starch, reflecting an increase in gel strength. These findings demonstrate that B-type starch is more sensitive to UMF than A-type starch. This study provides foundational data on the effects of UMF treatment on different crystalline starches, aiming to explore its potential applications in food and industrial fields.

A Review of Electromagnetic Fields in Cellular Interactions and Cacao Bean Fermentation

The influence of magnetic fields on biological systems, including fermentation processes and cocoa bean fermentation, is an area of study that is under development. Mechanisms, such as magnetosensitivity, protein conformational changes, changes to cellular biophysical properties, ROS production, regulation of gene expression, and epigenetic modifications, have been identified to explain how magnetic fields affect microorganisms and cellular processes. These mechanisms can alter enzyme activity, protein stability, cell signaling, intercellular communication, and oxidative stress. In cacao fermentation, electromagnetic fields offer a potential means to enhance the sensory attributes of chocolate by modulating microbial metabolism and optimizing flavor and aroma development. This area of study offers possibilities for innovation and the creation of premium food products. In this review, these aspects will be explored systematically and illustratively.

Regulation effect of magnetic field combined with low temperature storage on postharvest quality and cell wall pectic-polysaccharide degradation of Clausena lansium (Lour.) Skeels

This study investigated the regulation effect of magnetic field combined with low temperature storage on postharvest quality and cell wall pectic-polysaccharide degradation of wampee stored for 15 d at 4 °C and 15 °C. Results showed that magnetic field combined with low temperature storage reduced browning rate of fruit after 15 d storage, but its effect on weight loss rate and total soluble solids (TSS) did not surpass that of storage temperature. Interestingly, contents of flavonoid, total phenols and malondialdehyde (MDA) were also lowered at varying degrees by combined treatment. Furthermore, molecular weight distribution and monosaccharide compositions of cell wall pectic-polysaccharides were also affected, which resulted from the coordinated action of cell wall pectin-degrading enzymes. The activities of these enzymes during storage, including polygalacturonase (PG), pectin methylesterase (PME) and β-galactosidase (β-Gal) in treated wampee decreased. These findings suggested that magnetic field combined with low temperature storage was an effective technology and had great potential in preservation of postharvest wampee in future.

Atomic Force Microscopy Study of the Long-Term Effect of the Glycerol Flow, Stopped in a Coiled Heat Exchanger, on Horseradish Peroxidase

Glycerol is employed as a functional component of heat-transfer fluids, which are of use in both bioreactors and various biosensor devices. At the same time, flowing glycerol was reported to cause considerable triboelectric effects. Herein, by using atomic force microscopy (AFM), we have revealed the long-term effect of glycerol flow, stopped in a ground-shielded coiled heat exchanger, on horseradish peroxidase (HRP) adsorption on mica. Namely, the solution of HRP was incubated in the vicinity of the side of the cylindrical coil with stopped glycerol flow, and then HRP was adsorbed from this solution onto a mica substrate. This incubation has been found to markedly increase the content of aggregated enzyme on mica-as compared with the control enzyme sample. We explain the phenomenon observed by the influence of triboelectrically induced electromagnetic fields of non-trivial topology. The results reported should be further considered in the development of flow-based heat exchangers of biosensors and bioreactors intended for operation with enzymes.

Improving microbial production of value-added products through the intervention of magnetic fields

The magnetic field application is emerging as an auxiliary physical strategy to facilitate rapid biomass accumulation and intracellular production of compounds. However, the underlying mechanisms and principles governing the application of magnetic fields for microbial growth and biotransformation are not yet fully understood. Therefore, a better understanding of interdisciplinary technologies integration, expanded magnetic field application, and scaled-up industrial implementation is crucial. In this review, the magnetic field characteristics, magnetic field-assisted fermentation devices, and the working mechanism of magnetic field have been reviewed comprehensively from both physical and microbiological perspectives. The review suggests that magnetic fields affect the biochemical processes in microorganisms by mediating nutrient transport across membranes, electron transfer during photosynthesis and respiration, enzyme activity and gene expression. Moreover, the recent advances in magnetic field application for microbial fermentation and conversion in biochemical, food and agricultural fields have been summarized.

Regulation mechanism of magnetic field on pectinase and its preliminary application in postharvest sapodilla (Manilkara zapota)

In this study, regulation mechanism of magnetic field on pectinase was investigated and it was preliminarily applied in postharvest sapodilla. Results indicated pectinase activity decreased by 44 % when treated by magnetic field (3 mT, 0.5 h) with kinetic parameters V_max/K_m decreasing from 0.799 to 0.366 min. The optimal temperature (48 °C) and pH (4.8) of pectinase was not altered by magnetic field but Ca²⁺ at 0.05 mol/L strengthened its regulation effect. Ultraviolet and fluorescence spectra suggested tyrosine and tryptophan residues in treated pectinase became more hydrophobic while opposite in phenylalanine. CO, CNH, COO^- groups in pectinase were also influenced, resulting in decreased β-sheet (from 53 % to 49 %), increased random coil (from 20 % to 22 %) and β-turn content (from 27 % to 29 %). More importantly, the firmness of treated sapodilla remained 45 % of maximum at 12 days' storage. Our findings provided new insights to illustrate the role of magnetic field in fruit preservation.

Stopped Flow of Glycerol Induces the Enhancement of Adsorption and Aggregation of HRP on Mica

Glycerol is a usable component of heat-transfer fluids, and is thus suitable for the use in microchannel-based heat exchangers in biosensors and microelectronic devices. The flow of a fluid can lead to the generation of electromagnetic fields, which can affect enzymes. Herein, by means of atomic force microscopy (AFM) and spectrophotometry, a long-term effect of stopped flow of glycerol through a coiled heat exchanger on horseradish peroxidase (HRP) has been revealed. Samples of buffered HRP solution were incubated near either the inlet or the outlet sections of the heat exchanger after stopping the flow. It has been found that both the enzyme aggregation state and the number of mica-adsorbed HRP particles increase after such an incubation for 40 min. Moreover, the enzymatic activity of the enzyme incubated near the inlet section has been found to increase in comparison with that of the control sample, while the activity of the enzyme incubated near the outlet section remained unaffected. Our results can find application in the development of biosensors and bioreactors, in which flow-based heat exchangers are employed.

Production, Kinetic/Thermodynamic Study, and Evaluation of the Influence of Static Magnetic Field on Kinetic Parameters of β-Fructofuranosidase from Aspergillus tamarii Kita UCP 1279 Produced by Solid-State Fermentation

β-fructofuranosidases (FFases) are enzymes involved in sucrose hydrolysis and can be used in the production of invert sugar and fructo-oligosaccharides (FOS). This last is an important prebiotic extensively used in the food industry. In the present study, the FFase production by Aspergillus tamarii Kita UCP 1279 was assessed by solid-state fermentation using a mixture of wheat and soy brans as substrate. The FFase presents optimum pH and temperature at 5.0–7.0 and 60 °C, respectively. According to the kinetic/thermodynamic study, the FFase was relatively stable at 50 °C, a temperature frequently used in industrial FOS synthesis, using sucrose as substrate, evidenced by the parameters half-life (115.52 min) and D-value (383.76 min) and confirmed by thermodynamic parameters evaluated. The influence of static magnetic field with a 1450 G magnetic flux density presented a positive impact on FFase kinetic parameters evidenced by an increase of affinity of enzyme by substrate after exposition, observed by a decrease of 149.70 to 81.73 mM on Km. The results obtained indicate that FFases present suitable characteristics for further use in food industry applications. Moreover, the positive influence of a magnetic field is an indicator for further developments of bioprocesses with the presence of a magnetic field.

AFM Investigation of the Influence of Steam Flow through a Conical Coil Heat Exchanger on Enzyme Properties

The present study is aimed at the revelation of subtle effects of steam flow through a conical coil heat exchanger on an enzyme, incubated near the heat exchanger, at the nanoscale. For this purpose, atomic force microscopy (AFM) has been employed. In our experiments, horseradish peroxidase (HRP) was used as a model enzyme. HRP is extensively employed as a model in food science in order to determine the influence of electromagnetic fields on enzymes. Adsorption properties of HRP on mica have been studied by AFM at the level of individual enzyme macromolecules, while the enzymatic activity of HRP has been studied by spectrophotometry. The solution of HRP was incubated either near the top or at the side of the conically wound aluminium pipe, through which steam flow passed. Our AFM data indicated an increase in the enzyme aggregation on mica after its incubation at either of the two points near the heat exchanger. At the same time, in the spectrophotometry experiments, a slight change in the shape of the curves, reflecting the HRP-catalyzed kinetics of ABTS oxidation by hydrogen peroxide, has also been observed after the incubation of the enzyme solution near the heat exchanger. These effects on the enzyme adsorption and kinetics can be explained by alterations in the enzyme hydration caused by the influence of the electromagnetic field, induced triboelectrically by the flow of steam through the heat exchanger. Our findings should thus be considered in the development of equipment involving conical heat exchangers, intended for either research or industrial use (including miniaturized bioreactors and biosensors). The increased aggregation of the HRP enzyme, observed after its incubation near the heat exchanger, should also be taken into account in analysis of possible adverse effects from steam-heated industrial equipment on the human body.

Atomic Force Microscopy Study of the Effect of an Electric Field, Applied to a Pyramidal Structure, on Enzyme Biomolecules

The influence of an external constant strong electric field, formed using a pyramidal structure under a high electric potential, on an enzyme located near its apex, is studied. Horseradish peroxidase (HRP) is used as a model. In our experiments, a 27 kV direct current (DC) voltage was applied to two electrodes with a conducting pyramidal structure attached to one of them. The enzyme particles were visualized by atomic force microscopy (AFM) after the adsorption of the enzyme from its 0.1 µM solution onto mica AFM substrates. It is demonstrated that after the 40 min exposure to the electric field, the enzyme forms extended structures on mica, while in control experiments compact HRP particles are observed. After the exposure to the electric field, the majority of mica-adsorbed HRP particles had a height of 1.2 nm (as opposed to 1.0 nm in the case of control experiments), and the contribution of higher (>2.0 nm) particles was also considerable. This indicates the formation of high-order HRP aggregates under the influence of an applied electric field. At that, the enzymatic activity of HRP against its substrate 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) remains unaffected. These results are important for studying macroscopic effects of strong electromagnetic fields on enzymes, as well as for the development of cellular structure models.

The Effect of a Dodecahedron-Shaped Structure on the Properties of an Enzyme

In this research, the influence of a dodecahedron-shaped structure on the adsorption behavior of a horseradish peroxidase (HRP) enzyme glycoprotein onto mica substrates was studied. In the experiments, samples of an aqueous HRP solution were incubated at various distances (0.03 m, 2 m, 5 m, and control at 20 m) from the dodecahedron surface. After the incubation, the direct adsorption of HRP onto mica substrates immersed in the solutions was performed, and the mica-adsorbed HRP particles were visualized via atomic force microscopy (AFM). The effect of the increased HRP aggregation was only observed after the incubation of the enzyme solution at the 2 m distance from the dodecahedron. In addition, with respect to the control sample, spectrophotometric measurements revealed no change in the HRP enzymatic activity after the incubation at any of the distances studied. The results reported herein can be of use in the modeling of the possible influences of various spatial structures on biological objects in the development of biosensors and other electronic equipment.

Effect of static magnetic field treatment on the germination of brown rice: Changes in α-amylase activity and structural and functional properties in starch

The study aimed to explore the stimulating effect of static magnetic field (SMF) treatment on germinated brown rice (GBR) by monitoring changes in α-amylase activity and structural and functional properties of starch. Brown rice was exposed to SMF (10 mT, 60 min, 25 °C) and then germinated for 0 h -72 h at 30 °C. Compared with the control, SMF treatment improved α-amylase activity (15.2%), leading to the hydrolysis of starch into reducing sugar (8.2%) and increasing the germination rate (9.7% -158.8%), shoot length (9.1% -87.3%), root length (19.2% -110.0%), and fresh weight (0.9% -16.5%). In view of the properties of starch, SMF treatment also altered the surface microstructure, induced partial losses of birefringence, exerted no significant effect on the crystalline type, slightly increased the gelatinization temperatures, and significantly decreased the peak viscosity. This study suggested that SMF could serve as a prospective technique for GBR products processing.

Prospects and application of ultrasound and magnetic fields in the fermentation of rare edible fungi

Ultrasound has the potential to be broadly applied in the field of agricultural food processing due to advantages such as environmental friendliness, low energy costs, no need for exogenous additives and ease of operation. High-frequency ultrasound is mainly used in medical diagnosis and in the food industry for the identification of ingredients and production line quality testing, while low-frequency ultrasounds is mainly used for extraction and separation, accelerating chemical reactions, auxiliary microbial fermentation and quality enhancement in food industry. Magnetic fields have many advantages of convenient use, such as non-toxic, nonpolluting and safe. High-intensity pulsed magnetic fields are widely used as a physical non-thermal sterilization technology in food processing, while weak magnetic fields are better at activating microorganisms and promoting their growth. Ultrasound and magnetic fields, due to their positive biological effects, have a wide range of applications in the food processing industry. This paper provides an overview of the research progress and applications of ultrasound and magnetic fields in food processing from the perspectives of their biological effects and mechanisms of action. Additionally, with the development and application of physical field technology, physical fields can now be used to provide significant technical advantages for assisting fermentation. Suitable physical fields can promote the growth of microbial cells, improve mycelial production and increase metabolic activity. Furthermore, the current status of research into the use of ultrasound and magnetic field technologies for assisting the fermentation of rare edible fungi, is discussed.

Effect of Spherical Elements of Biosensors and Bioreactors on the Physicochemical Properties of a Peroxidase Protein

External electromagnetic fields are known to be able to concentrate inside the construction elements of biosensors and bioreactors owing to reflection from their surface. This can lead to changes in the structure of biopolymers (such as proteins), incubated inside these elements, thus influencing their functional properties. Our present study concerned the revelation of the effect of spherical elements, commonly employed in biosensors and bioreactors, on the physicochemical properties of proteins with the example of the horseradish peroxidase (HRP) enzyme. In our experiments, a solution of HRP was incubated within a 30 cm-diameter titanium half-sphere, which was used as a model construction element. Atomic force microscopy (AFM) was employed for the single-molecule visualization of the HRP macromolecules, adsorbed from the test solution onto mica substrates in order to find out whether the incubation of the test HRP solution within the half-sphere influenced the HRP aggregation state. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was employed in order to reveal whether the incubation of HRP solution within the half-sphere led to any changes in its secondary structure. In parallel, spectrophotometry-based estimation of the HRP enzymatic activity was performed in order to find out if the HRP active site was affected by the electromagnetic field under the conditions of our experiments. We revealed an increased aggregation of HRP after the incubation of its solution within the half-sphere in comparison with the control sample incubated far outside the half-sphere. ATR-FTIR allowed us to reveal alterations in HRP's secondary structure. Such changes in the protein structure did not affect its active site, as was confirmed by spectrophotometry. The effect of spherical elements on a protein solution should be taken into account in the development of the optimized design of biosensors and bioreactors, intended for performing processes involving proteins in biomedicine and biotechnology, including highly sensitive biosensors intended for the diagnosis of socially significant diseases in humans (including oncology, cardiovascular diseases, etc.) at early stages.